They attack with a distinctive buzzing sound that travels quite far. Considering they only take some of their prey's blood, the noise often draws those wishing to scavenge on their leavings

They aren't parasites, but symbiotic creatures that live on and with underdark horrors like Hook Horrors and Umber Hulks. The sign of a stirge is an indicator of one of these great beasts

The stirge is not a grown creature, it is in larval form. It collects blood for the coming change, and enters a pupae stage for less than a week. It emerges from its old shell as a combination of the creature and insect like features of the stirge

A character can also attempt to dislodge a strige by tensing their muscles. Each round they must succeed on a constitution check. On the third round, the stirge bursts from the blood they have taken in. It is a common game among barbarians

Goblins are quite fond of adding stirge to stew, the more bloody the better

They are also popular with the blood drinking undead

They are often kept as pets or allies, intentionally or unintentionally, by other creatures, attacking a minute or two after the creatures they are allied with do. They often are able to feed and flee this way before any attention is paid to them

They are the spawn of an insane vampire who desired living servants

Stirges were once humans who were transformed into these as punishment

They are viewed as harbringers of war and strife

Blood drank from a stirge sac can heal the injured. What is less commonly known is that it is also highly addictive

They can sense mutations and diseases and will avoid those with tainted blood

Certain types of blood are extremely attractive to stirges and they will favor those targets over all others

Stirges are lulled to sleep by mournful polyphonic dirges

They were originally crafted by vampiric wizards to throw hunters of the undead off track

They were the minions of evil wizards who bred them by the millions and released them against enemy armies arrayed against them.

The stirge uses blood to fuel a bizarre alchemical process in its bloated para-abdomen. This process is how the gas it uses to fly is produced

Stirges are a cross between a leech and a bat and have no relation to insects or mosquitoes

The stirge is actually completely an insect, what appears to be hair are actually just sensing fibers

The stirge is a larval form of a Stirgeon, a highly intelligent creature, specializing in the science of blood, hematology. Many underdark denizens consider it superior surgeon to even the Xixchil

Chirugeons use stirge cages to drain excess humors from patients. Varieties of stirge such as blood, black bile, yellow bile, and phlegm are known

Blood stirges are the only ones who can fly and are fond of liver

Phlegm stirges swim, and try to drain the lungs and brains of their victims through the nose

Yellow Bile stirges propel themselves with jets of burning gasses, and are very quick. They eat as fast as they move, devouring a spleen in 1-5 rounds. This can be fatal

Black Bile stirges are wormlike and live in earth, soil, and rock, looking to enter bodies through the anus or urethra, then eating the gall bladder. Victims become despondent, sleepless and irritable, but they live

Stirge eggs are laid in carcasses. They are laid when the stirge feeds

When a stirge attacks, they attempt to squeeze between the armor and the skin

Stirges are annoyance made manifest. They will take whatever form of vermin is most suitably annoying

They are just subterranean hummingbirds and completely harmless. Their abilities and appearance has been exaggerated because they spook adventurers very eaisly when they dart into torchlight, and no one is going to admit once they get back home that they were scared by a tiny harmless bird

Stirges are technically tiny pterodactyls

Stirges will continue to feed, even after satiation. They can hold more blood than a man. Much more than that, and their membrane ruptures, leading to sacks of pigs blood as a common tactic against stirges

Stirges are the key ingredient in Instant Blutwurst, a beloved winter dish of the Dzhungaznian Dwarves of Dheoghnunn

Stirge eggs pickled in brine are known as stony mountain caviar

Stirges have three wings and an organic flywheel to assist them in flying, hence their excellent maneuverability

Telling people that stirges eat your blood is simply adventurers whitewashing the truth for the townsfolk. They actually have a razor-sharp maw and specialize in eating your face off

Stirges are sentient assemblages of stringy worms, cooperating for the greater good. They attempt to get ingested to take control of their victims, turning them into reckless adventurers who will get eaten by a dragon. It is in the dragon's duodenum that a stirge matures, laying eggs that hatch into dragon-dung-worms

Stirges are bio-engineered syringes, given small wings to be at had for the enterprising surgeon. Their progenitors have long since died off, and they have adapted to take the blood of anyone nearby in an attempt to discern their health. Sadly, without the help of an authorized medical representative, all the tests are inconclusive and must be repeated

Every time a mortal dies from an supremely selfish act, a swarm of stirges is born. Kings of greed spawn dire stirge queens, who brood thousands more

Jungle goblins use stirge bones in the fruit gruel they feed their children, for crunch and marrow; this is simliar to the method plains goblins feed their children tigre nails in a bowl of rotten goat crud

Stirges do not drain blood. They don't drain anything. The needle mouth is actually an ovipositor.

Stirges are magical creatures used to obtain the essence of creatures for use in sympathetic magic. Bat-like stirges exist and seek out hair; this is the source of the old urban legend]

Stirges are the physical form of malaria-spirit, they infect their targets with a magical disease and then feed on that

Stir-inges are magical syringes made from stirge ovipositors

The belief that stirges deposit eggs with their proboscis is wrong, they actually deposit mutagenic sperm, which impregnates the host tissue. This created a 'stirgiform grub' which absorbs genetic information from its host before erupting from the body

Stirge guano is red and grainy. When dry it hardens into a clay like substance that is flammable and useful as fertilizer

Corpses drained of all blood are also very flammable. The stirge secretes a substance to maintain the blood pressure in the vascular system to allow it to easily drink. This substance plus the desiccation of the body make fully drained corpses very flammable.

When the first demon army came to make war in the marshes, the mosquitoes fed, and were changed.﻿

Kabraxis, the Demon of Lust, has a thousand detachable members that swap fluids with whole crowds of worshiping cultists during a ceremony. Some of them can't fit back on the demon, as more are constantly growing. Any site with stirge is a site where cultists had congress with their dark master.

They are aberrant bats that lair in the thousands underground. Their digestive system is extremely efficient, causing them under normal circumstances to only need to feed a small sip.

The Psychic Wizards of Marnbayzie got so proficient playing darts they needed to make the game interesting. They created darts that could fly of their own accord, with enough mind to give mentalists another venue for winning. Lazy and stylish, the foppish wizards eventually adapted the darts to fetch them drinks, drawing from the bar and squirting into cups.

When STDs, madness, mutation, and furious former lovers finished with the order, enough of the stirge survived to spread and become a real problem. Still, a wizard wearing a yellow and silver robe may find that stirge still have enough racial memory to want to fill their cups for them. Better hope wine is handy.﻿

The first stirge were created when a profoundly powerful wizard used a Power Word originally designed to turn dragon teeth into warriors. Crippled and desperate, the wizard cast it on a still-living dragon, whose needle-sharp teeth tore loose with wads of gum tissue and bone, desperate and insane with agony, stabbing and drinking to assuage the pain they still felt through the sundered nerves.

The Chupacabra is a ground based large relative of the stirge

The dragon was immortal, and captured, and its teeth suffer and feed still. If the dragon dies, perhaps all the stirge die too. If the stirge ever proliferate to a certain point, perhaps the dragon will become strong enough to escape and reunite with them.﻿

A min-maxing wizard character was not content to only throw 3 darts a round, or to be stuck without armor. After decades of casting animating magic on the same darts, eventually they were imbued with the magic. The final step was when the wizard fell into the pool that animated inanimate objects, and the darts came alive.

"It's not armor," the player protested, strapping cages to chest, back, arms, legs. The cages filled with the now-living darts, who returned to their master. Until the DM had enough and an ogre mage charmed the lot of them and drained the enterprising munchkin dry. Now they are feral.﻿

Stirge are the carrier pigeons of the Stygian Suburb. Their wings are uniquely suited to carry demonic script, and they are instinctively eager to please demons. Swarms gather in the palaces where the demons hold massive social events like gala balls, feasts, and hunts.

The strix is a vampiric bird, a cousin of the stirge

The stirge is the only form a shapeshifting witch can take

It is the height of fashion for demons and tieflings to have "blood buttons" with a few drops of a friend or enemy's blood in the center; the stirge pecks the button the demon chooses, then homes to that demon with the message.﻿

They attack sleeping victims without them noticing, for a stirge bite is painless.

Kyvash War College is famed for its Biomunitions Chair, funded by the Zephrox Mercenary Guild. One of their more popular sub-projects was sponsored by the neogi, who wanted a way to weaken eggredex beasts (who were immune to poison and mind control) to make them easier to capture and sell to wealthy nobles. The stirge nest was portable, and the blood the stirge took weakened the strange circulatory system of the eggredex beast (who operated on hydraulic principles) so they could be folded and taken quietly. When the eggredex beasts went extinct, the stirge were re-purposed for "scorched earth" campaigns to deter resettling in the dimension wars.﻿

Mr. Gygax the demiurge
Happily created the stirge -
It's like a mosquito
Except you're finito
If your paths should ever converge.

Stirges are frequently mistaken for vampires based on their method of feeding

Garlic and holy water infuriate stirges, causing them to fly into a rage and attack until death

Stirge are actually the attack helicopters of a particularly repugnant brand of sprite. Their fuel is blood. Don't believe it? Twist off the head, and in the chamber between the eyes there is an extraordinarily furious blue person half the size of your pinkie finger. These sprites are on a religious quest to kill nosy people, and they are an off-shoot of the species that manages will-o-wisps remotely with psychic powers. Their rivalry is legendary.

They do not attack. They simply track prey, waiting. Once a fight begins, they attack everyone, feeding on those that are damaged. As soon as the fight is over, they retreat again, up into the trees, following and waiting again.

Stirges hunt people by softly calling out their name. This rhythmic chant entrances the victim, putting them into a stupor and making them unaware of their environment. The stirge then has free reign to do what they wish to the victim.

When the Zerg first came to this world, bats were caught in the creep. Most died. A few survived, but the fast and loose mutagenic properties of the creep tied them to the hive mind and warped them into monsters.﻿

Sites that have heavy stirge infestations often keep small mammals in cages at the top of poles around town to deter them feeding on humans and to provide target practice to the locals

The greatest of the vampire necromancers weaponized his blood, so that every drop shed would twirl free, spinning out wings and starvation, and attack on his behalf. He was eventually slain, but his creations thrived and grew large. They are able to breed true; they share the same blood, after all.﻿

The dire strige is the size of an elder pot-bellied pig, has six wings and a blood draining proboscis at either end

In the warrens of Moloko, they murmur of the hydra stirge created by the mad mage Mulana of Mulenbach

"I have invented a biomechanical creature based on the stirge, which is attracted to naphta or rock-oil, the raw ingredient required for the activation of the phlogiston in the internal explosion engine. I believe this oil-irge will lead to a time of great plenty and good for all dwarven-kind, freeing us from toil and bringing us a period of peace, plenty and oneness with nature." - Ishtvan Shentdizely of the Blackrock Dwarve Corporation﻿

They were designed by alchemists at autonomous blood sample collectors, but have since escaped and bred true. The ancient scent lore of the alchemists can still be used to tame and direct the stirges, if they could be discovered and deciphered

Stirges can't withdraw their proboscises from padded armor and will bloat up like honeypot ants

Rothe blood is toxic to stirges and they avoid anyone with the musk of the rothe. That is unfortunately true in general

Stirges originally were fruit eaters, but they were trapped in a cave after an earthquake, opening a path to the underworld. They were forced to adapt to drinking blood to survive. Sadly this trait bred true and almost all the harmless fruit eaters are dead

Stirges quickly succumb to bad air, like canaries

Fire-roasted strige is best when served fully bloated, otherwise it's dry and chewy

Stirges always travel in flocks which are multiples of 8. This is because they are the tips of the tentacles of an ethereal octopus creature, which partially extrudes itself onto our plane to feed. This is why stirges have an out-sized thirst

Stirges actually prefer red wine over blood.

Tying stirges together is a favorite goblin pastime.

A healing stirge is an enchanted bound stirge that injects the stored blood into your body. You have to pierce your skin and squeeze the blood sac to get the blood to inject. This bursts delicate membranes in the stirges head, but heals you 2-16 points of damage

Bound together stirges are used to play a goblin children's game called Sip-sip. The players run in circles easily avoiding the stirges, but usually crashing into one another and making an easier target for the "Sip-sip"

Stirge-owls serve the underworld goddess and her minions. Everyone from her gatekeepers to her vampire throne bearers use stirge-owls as messengers and shock troops. Underworld stirges can both be larger than normal and hit creatures only hit with magical weapons.

Stirge beaks make excellent quill tips for scribing scrolls.﻿

Stirge eyeballs are heavy and shiny and make good sling bullets.﻿

Stirges are used by Drawangari doctors to purge bad humours from sick people. A wild stirge bite has a 25% chance of having a Cure disease effect on the victim.﻿

Stirge enzymes convert blood into a thin, ichor-like fluid and can be used to kill vampires, as they rapidly convert the blood a vampire has ingested into stirgeon juice.﻿

Some less scrupulous Drawangari doctors reuse stirges rather than dispose of them as per custom. These "recycled stirges" have a 25% (low end) chance of Cure disease and 25% (high end) chance of Cause disease.﻿

In enlightened Drawangari city states, city authorities have taken to providing single-use neutered, short-lived may-stirges pre-filled with troll blood to Tee addicts.﻿

Halflings of the Upper Blue Dowager clans of Peenkemoende have taken to using trained carrier stirges to harvest troll blood, which is used by humanoid and elven addicts to get a high and temporary regeneration ( though as the saying goes, "shoot tee and you bee fick ass troll" ).

Black-and-blue market dealers often mix troll blood with chicken blood to increase their margins, though this generally destroys the regenerative properties. On the market this product is often called chee-tee (cheaty).﻿

Boiling a stirge that is well fed makes a delicious blood pudding

Combat Techniques

Flock blindness: When three or more stirges affect a single target, their vision is obscured for the round causing them to act as if they are blinded

Armor Crawl: On a strike, the strige may worm its way under the armor. This protects the stirge from damage, giving it the AC of the wearers armor and insuring that any hit that hurts it, hurts the wearer for an equal amount

Eye Stab: Some Stirges are unsatified with blood, and with to drink fluid out of the eyes. They land on the target on the first turn, move to the eye on the second, and on the third turn make a strike into the eyeball, with a penalty to hit of -4 versus the armor class of the eye (usually 10 unless wearing a helm with eye protection) On a successful hit, the victim must save versus paralyzation or become shaken by the pain and the eye is seriously damaged, causing partial blindness. (-4 to hit with ranged attacks, -2 on attacks/vision based perception, -1 on surprise)

Variations

Phase Stirge: In addition to the standard phase characteristics, they can drain blood from targets up to 10 m (30') away, without needing to touch the victim.

Jungle Stirge: Twice the size of a normal stirge, and has a paralyzing venom when it strikes

Desert Stirge: A flightless hopping creature that attacks it's prey somewhat like a large flea. They can burrow beneath the sand and travel with a movement rate of 6" underground

Ghost Stirge: A stirge that died from lack of blood. They ooze ectoplasm which sucks the life from targets as well as draining blood as normal. They return to life again and again until their remains are bathed in warm blood

Two-headed: This variety has an additional head. This grants an additional attack as well as reducing the chances of surprise

Enraged Stirge Whip: This creature does not feed with a probosis, but instead has 4 long (20') whiplike limbs that attach and drain blood from multiple creatures. The whips have AC 3 and 10 hit points each. It normally attaches itself to a cave wall or surface before attacking. It can attack itself to a surface with an effective strength of 20. It flies and is small instead of tiny. They hunt in packs.

Swamp: These are much smaller than normal (about the size of a half dollar) but they travel in huge swarms. They hunt at dusk.

The ecology series is a crowdsourced series of articles, and contributors can be found on google+ under the hashtag #crowdecology. They are limited posts, but following me on G+ will allow you to see them. All artwork is credited where the artist could be found. Classic ecology articles from Dragon magazine are used both for reference and inspiration; the whole impetus of the idea was to create 'classic' ecology articles that are actually useful. Let's Read the Monster Manual by Noisms is also a source of inspiration.